I couldn't see anything significant in the log. But I found that when I disable "proxy_intercept_errors on" in Nginx reverse proxy, the 401 error disappears. I can login but the page does not load the menus correctly. When the access is done via ip and not by name the menus appear correctly. It seems that some configuration must be done in Gestioip's Apache to accept proxy redirection.
I installed gestioip using docker containers. I use Nginx proxy redirect to access it. However, a 401 error is displayed. Should I change some configuration in the gestioip container?